Generally known apparatuses for lowering the electrical resistance of an impurity-doped p-type semiconductor include an electron-beam irradiation apparatus described in, for example, “Present Situation and Future of GaN-Based Light-Emitting Devices” (Applied Physics, Vol. 65, No. 7, 1996).
In such a conventionally employed electron-beam irradiation apparatus, a sample (e.g., a semiconductor which is to be irradiated with electron beams) is irradiated with electron beams in a vacuum atmosphere.